The invention is based on a fuel injection pump for internal combustion engines. In a fuel pump of this type known from German Patent DE-OS 39 10 794 Al a separate fuel injection apparatus is associated with each cylinder of the engine to be fed; this apparatus comprises a pump piston guided in a cylinder liner and in it defining a pump work chamber that communicates with the injection point in the combustion chamber of the engine and which is axially driven via a roller tappet of a cam drive counter to the force of a restoring spring. In order to form this single pump element in the simplest manner possible, it does not have its own housing, but rather is so inserted with its pump cylinder into the housing of the engine that the engine housing itself serves as the pump housing, both as a fuel-carrying chamber and as a mechanical guide and support.
Because the roller tappet is guided directly in the engine housing and because of the attendant friction between the parts, the known fuel injection pump experiences increased wear, which can result in the need for replacement of the roller tappet, in addition to cost-intensive remachining of the engine housing.
DE-PS 37 28 961 has already made known a fuel injection pump in the form of a plug-in pump in which the roller tappet of the cam drive slides in a bush slid onto the cylinder liner; however, this particular bush is a self-supporting housing part which has a flange that comes to rest against the bore in the housing of the engine and determines the installed position of the plug-in pump. This pump points into an internal chamber of the engine housing which receives the cam drive for the plug-in pump and has the guide piece for the roller tappet there. Consequently the plug-in pump deviates from the aforementioned fuel injection pump in that it has a housing that is costly to fabricate, that when wear occurs must be replaced or remachined and rebuilt with a matched roller tappet.